Add second domain

I have set up ZCS with one domain. Our other domain is still being hosted on a separate non-Zimbra box. I want to begin the process of migrating the other domain over to the Zimbra box. However, as soon as I add the other domain name, mail to that domain will no longer be delivered to the other box. I have /etc/hosts with the ip of the other box for that domain. If I do a ping it does ping to the other box, but zimbra seemingly won't release the mail to the other domain. What am I missing?
Thanks!

I have set up ZCS with one domain. Our other domain is still being hosted on a separate non-Zimbra box. I want to begin the process of migrating the other domain over to the Zimbra box. However, as soon as I add the other domain name, mail to that domain will no longer be delivered to the other box. I have /etc/hosts with the ip of the other box for that domain. If I do a ping it does ping to the other box, but zimbra seemingly won't release the mail to the other domain. What am I missing?
Thanks!

Go to the wiki and read the details of Split Domain - that's what you'll need.

Hm, I don't think this is the situation I'm talking about. This document assumes you have 1 domain (example.com) and some of the users are on Zimbra and some are still on another mail server.
In my case I have 2 domains: example.com and domain.com. example.com is on Zimbra and running. I want to add domain.com to Zimbra, but any mail for domain.com should go to the existing domain.com mail server.